Removing Blender Game Engine from Blender 2.8

Folders removed entirely:
* //extern/recastnavigation
* //intern/decklink
* //intern/moto
* //source/blender/editors/space_logic
* //source/blenderplayer
* //source/gameengine

This includes DNA data and any reference to the BGE code in Blender itself.
We are bumping the subversion.

Pending tasks:
* Tile/clamp code in image editor draw code.
* Viewport drawing code (so much of this will go away because of BI removal
  that we can wait until then to remove this.

source/blender/python/mathutils/mathutils.h

@@ -62,7 +62,7 @@ enum {
 	float *_data;               /* array of data (alias), wrapped status depends on wrapped status */            \
 	PyObject *cb_user;          /* if this vector references another object, otherwise NULL,                     \
 	                             * *Note* this owns its reference */                                             \
-	unsigned char cb_type;      /* which user funcs do we adhere to, RNA, GameObject, etc */                     \
+	unsigned char cb_type;      /* which user funcs do we adhere to, RNA, etc */                                 \
 	unsigned char cb_subtype;   /* subtype: location, rotation...                                                \
 	                             * to avoid defining many new functions for every attribute of the same type */  \
 	unsigned char flag          /* wrapped data type? */                                                         \